{{ $tocLevels := default (default 6 .Site.Params.BookToC) .Params.BookToC }}
{{ if and $tocLevels .Page.TableOfContents }}
  <aside class="book-toc level-{{$tocLevels}} fixed">
    <div class="qrCode">
      <div>
        <img src="/img/wechat.jpg">
        <p> {{ .Page.TableOfContents }}</p>
      </div>
    </div>
  </aside>
{{ end }}
